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PKC regulation of ion channels: The involvement of PIP 2. J Biol Chem 2022; 298:102035. [PMID: 35588786 PMCID: PMC9198471 DOI: 10.1016/j.jbc.2022.102035] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/24/2022] Open
Abstract
Ion channels are integral membrane proteins whose gating has been increasingly shown to depend on the presence of the low-abundance membrane phospholipid, phosphatidylinositol (4,5) bisphosphate. The expression and function of ion channels is tightly regulated via protein phosphorylation by specific kinases, including various PKC isoforms. Several channels have further been shown to be regulated by PKC through altered surface expression, probability of channel opening, shifts in voltage dependence of their activation, or changes in inactivation or desensitization. In this review, we survey the impact of phosphorylation of various ion channels by PKC isoforms and examine the dependence of phosphorylated ion channels on phosphatidylinositol (4,5) bisphosphate as a mechanistic endpoint to control channel gating.
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Zhang Y, Wang X, Zhang M, Lin X, Wu Q, Yang Y, Kong J, Ji P. The trophic effect of ciliary neurotrophic factor on injured masseter muscle in rat. IRANIAN JOURNAL OF BASIC MEDICAL SCIENCES 2015; 18:920-6. [PMID: 26526387 PMCID: PMC4620193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
OBJECTIVES Occlusal trauma is one of the most common forms of oral biting dysfunction. Long-term occlusal trauma could weaken the stomatognathic system; especially damage one's masticatory muscle. Through using the rat model, this study investigated the trophic effect of ciliary neurotrophic factor (CNTF) on injured masseter muscle. MATERIALS AND METHODS Male Wistar rats (n=36) were randomly divided into five experimental groups and one control group (6 rats per group). Animals in the experimental group were cemented modified crowns on their mandibular first molars to artificially induce occlusal trauma in 1, 3, 7, 14, and 28 days. Control group was sham-treated with forced mouth-opening for about 5 min, while no crowns were placed. After 28 days of treatment, all rats were euthanized and their masseter muscle was collected. Through immunofluorescence and real-time quantitative PCR, the expression of desmin, CNTF, and CNTFRα was investigated in rat masseter muscle. The microstructure of masseter muscle was observed by transmission electron microscope. RESULTS The expression of desmin showed a time-dependent decrease on traumatic and non-traumatic sides masseter, until reached the nadir at the 14(th) day, then restored to its normal level at the 28(th) day; however, the expression of CNTF and CNTFRα on the traumatic and non-traumatic sides increased from day 7, reached the peak at the 14(th) day, and returned to normal level on the 28(th) day. CONCLUSION CNTF, as an important neurotrophic factor, was tightly associated to the restoring of rat injured masseter muscle, which provides new target and treatment method for clinical application.
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Affiliation(s)
- Yujun Zhang
- Shandong Provincial Key Laboratory of Oral Biomedicine, College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Postcode: 250012
| | - Xiaohui Wang
- College of Stomatology, Taishan Medical College, Taian City, Shandong Province, China
| | - Mengmeng Zhang
- Shandong Provincial Key Laboratory of Oral Biomedicine, College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Postcode: 250012
| | - Xuefen Lin
- Shandong Provincial Key Laboratory of Oral Biomedicine, College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Postcode: 250012
| | - Qingting Wu
- Shandong Provincial Key Laboratory of Oral Biomedicine, College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Postcode: 250012
| | - Yingying Yang
- Shandong Provincial Key Laboratory of Oral Biomedicine, College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Postcode: 250012
| | - Jingjing Kong
- Shandong Provincial Key Laboratory of Oral Biomedicine, College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Postcode: 250012
| | - Ping Ji
- Shandong Provincial Key Laboratory of Oral Biomedicine, College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Postcode: 250012,Corresponding author: Ping Ji. College of Stomatology, Shandong University, Jinan City, Shandong Province, China. Tel: +86-0531-88382448;
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Gueret G, Guillouet M, Vermeersch V, Guillard E, Talarmin H, Nguyen BV, Rannou F, Giroux-Metges MA, Pennec JP, Ozier Y. [ICU acquired neuromyopathy]. ACTA ACUST UNITED AC 2013; 32:580-91. [PMID: 23958176 DOI: 10.1016/j.annfar.2013.05.011] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2012] [Accepted: 05/08/2013] [Indexed: 12/19/2022]
Abstract
ICU acquired neuromyopathy (IANM) is the most frequent neurological pathology observed in ICU. Nerve and muscle defects are merged with neuromuscular junction abnormalities. Its physiopathology is complex. The aim is probably the redistribution of nutriments and metabolism towards defense against sepsis. The main risk factors are sepsis, its severity and its duration of evolution. IANM is usually diagnosed in view of difficulties in weaning from mechanical ventilation, but electrophysiology may allow an earlier diagnosis. There is no curative therapy, but early treatment of sepsis, glycemic control as well as early physiotherapy may decrease its incidence. The outcomes of IANM are an increase in morbi-mortality and possibly long-lasting neuromuscular abnormalities as far as tetraplegia.
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Affiliation(s)
- G Gueret
- Pôle anesthésie réanimations soins intensifs blocs opératoires urgences (ARSIBOU), CHRU de Brest, boulevard Tanguy-Prigent, 29200 Brest, France; Laboratoire de physiologie, faculté de médecine et des sciences de la santé, EA 1274 (mouvement, sport santé), université de Bretagne-Occidentale, 22, avenue Camille-Desmoulins, 29200 Brest, France; Université européenne de Bretagne, 5, boulevard Laennec, 35000 Rennes, France.
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Guillard E, Gueret G, Guillouet M, Vermeersch V, Rannou F, Giroux-Metges MA, Pennec JP. Alteration of muscle membrane excitability in sepsis: Possible involvement of ciliary nervous trophic factor (CNTF). Cytokine 2013; 63:52-57. [DOI: 10.1016/j.cyto.2013.04.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2012] [Revised: 02/01/2013] [Accepted: 04/15/2013] [Indexed: 10/26/2022]
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Garcia N, Santafé MM, Tomàs M, Priego M, Obis T, Lanuza MA, Besalduch N, Tomàs J. Exogenous ciliary neurotrophic factor (CNTF) reduces synaptic depression during repetitive stimulation. J Peripher Nerv Syst 2012; 17:312-23. [DOI: 10.1111/j.1529-8027.2012.00419.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Rannou F, Leschiera R, Giroux-Metges MA, Pennec JP. Effects of lactate on the voltage-gated sodium channels of rat skeletal muscle: modulating current opinion. J Appl Physiol (1985) 2012; 112:1454-65. [DOI: 10.1152/japplphysiol.00944.2011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
During muscle contraction, lactate production and translocation across the membrane increase. While it has recently been shown that lactate anion acts on chloride channel, less is known regarding a potential effect on the voltage-gated sodium channel (Nav) of skeletal muscle. The electrophysiological properties of muscle Nav were studied in the absence and presence of lactate (10 mM) by using the macropatch-clamp method in dissociated fibers from rat peroneus longus (PL). Lactate in the external medium (petri dish + pipette) increases the maximal sodium current, while the voltage dependence of activation and fast inactivation are shifted toward the hyperpolarized potentials. Lactate induces a leftward shift in the relationship between the kinetic parameters and the imposed potentials, resulting in an earlier recruitment of muscle Nav. In addition, lactate significantly decreases the time constant of activation at voltages more negative than −10 mV, corresponding to an acceleration of Nav activation. The slow inactivation process is decreased by lactate, corresponding to an enhancement in the number of excitable Nav. In an additional series of experiments, lactate (10 mM) was only added to the petri dish, while the pipette remained sealed on the membrane area. With this approach, the electrophysiological properties of Nav were unaffected by lactate compared with the control condition. Altogether, these data indicate that lactate modulates muscle Nav properties by an extracellular pathway. These effects are consistent with an enhancement in excitability, providing new insights into the role of lactate in muscle physiology.
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Affiliation(s)
- F. Rannou
- Université de Brest, Faculté de Médecine et des Sciences de la Santé, EA 1274-M2S, Laboratoire de Physiologie
- CHU Brest, Service d'Explorations Fonctionnelles Respiratoires; and
- Université Européenne de Bretagne, Brest, France
| | - R. Leschiera
- Université de Brest, Faculté de Médecine et des Sciences de la Santé, EA 1274-M2S, Laboratoire de Physiologie
- Université Européenne de Bretagne, Brest, France
| | - M. A. Giroux-Metges
- Université de Brest, Faculté de Médecine et des Sciences de la Santé, EA 1274-M2S, Laboratoire de Physiologie
- CHU Brest, Service d'Explorations Fonctionnelles Respiratoires; and
- Université Européenne de Bretagne, Brest, France
| | - J. P. Pennec
- Université de Brest, Faculté de Médecine et des Sciences de la Santé, EA 1274-M2S, Laboratoire de Physiologie
- Université Européenne de Bretagne, Brest, France
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7
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Guillouet M, Gueret G, Rannou F, Giroux-Metges MA, Gioux M, Arvieux CC, Pennec JP. Tumor necrosis factor-α downregulates sodium current in skeletal muscle by protein kinase C activation: involvement in critical illness polyneuromyopathy. Am J Physiol Cell Physiol 2011; 301:C1057-63. [PMID: 21795525 DOI: 10.1152/ajpcell.00097.2011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Sepsis is involved in the decrease of membrane excitability of skeletal muscle, leading to polyneuromyopathy. This effect is mediated by alterations of the properties of voltage-gated sodium channels (Na(V)), but the exact mechanism is still unknown. The aim of the present study was to check whether tumor necrosis factor (TNF-α), a cytokine released during sepsis, exerts a rapid effect on Na(V). Sodium current (I(Na)) was recorded by macropatch clamp in skeletal muscle fibers isolated from rat peroneus longus muscle, in control conditions and after TNF-α addition. Analyses of dose-effect and time-effect relationships were carried out. Effect of chelerythrine, a PKC inhibitor, was also studied to determine the way of action of TNF-α. TNF-α induced a reversible dose- and time-dependent inhibition of I(Na). A maximum inhibition of 75% of the control current was observed. A shift toward more negative potentials of activation and inactivation curves of I(Na) was also noticed. These effects were prevented by chelerythrine pretreatment. TNF-α is a cytokine released in the early stages of sepsis. Besides a possible transcriptional role, i.e., modification of the channel type and/or number, we demonstrated the existence of a rapid, posttranscriptional inhibition of Na(V) by TNF-α. The downregulation of the sodium current could be mediated by a PKC-induced phosphorylation of the sodium channel, thus leading to a significant decrease in muscle excitability.
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Affiliation(s)
- Maité Guillouet
- Faculté de Médecine et des Sciences de la Santé, Laboratoire de Physiologie, Université de Brest, Brest, France
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Guillouet M, Gueret G, Rannou F, Giroux-Metges MA, Gioux M, Arvieux CC, Pennec JP. TNFα increases resting potential in isolated fibres from rat peroneus longus by a PKC mediated mechanism: involvement in ICU acquired polyneuromyopathy. Cytokine 2011; 56:149-52. [PMID: 21737299 DOI: 10.1016/j.cyto.2011.05.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2010] [Revised: 05/05/2011] [Accepted: 05/25/2011] [Indexed: 01/18/2023]
Abstract
BACKGROUND AND AIMS Our aim was to investigate the effect of TNFα on muscle resting potential (RP) and then in muscle excitability and to demonstrate another mechanism implicated in intensive care units (ICU) acquired polyneuromyopathy. METHODS Experiments were carried out on adult female Wistar rats. After isolation of muscle fibres from peroneus longus, influence of TNFα was tested on RP by using intracellular microelectrodes. Digoxin and chelerythrin were used to determine the mechanism of TNFα action. RESULTS First, we found that TNFα induced a concentration dependent increase of muscle RP and that this mechanism, which was blocked by digoxin, was due to an effect on the Na/K ATPase. As it was also blocked by chelerythrin it was concluded that this effect was mediated by PKC activation of the Na/K ATPase. CONCLUSIONS We demonstrated that TNFα leads to a PKC mediated increase in muscle RP. Depolarization needed to reach the threshold voltage for muscle action potential should then be higher and this could be involved in the decrease in muscle excitability observed in acquired polyneuromyopathy.
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Affiliation(s)
- Maité Guillouet
- CHU Brest, Pôle Anesthésie Réanimation, Université de Brest, Faculté de Médecine et des Sciences de la Santé, EA 4326, Laboratoire de Physiologie, Brest, F-29200, France
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9
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Sodium channel Na(V)1.5 expression is enhanced in cultured adult rat skeletal muscle fibers. J Membr Biol 2010; 235:109-19. [PMID: 20517693 DOI: 10.1007/s00232-010-9262-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2010] [Accepted: 05/10/2010] [Indexed: 12/19/2022]
Abstract
This study analyzes changes in the distribution, electrophysiological properties, and proteic composition of voltage-gated sodium channels (Na(V)) in cultured adult rat skeletal muscle fibers. Patch clamp and molecular biology techniques were carried out in flexor digitorum brevis (FDB) adult rat skeletal muscle fibers maintained in vitro after cell dissociation with collagenase. After 4 days of culture, an increase of the Na(V)1.5 channel type was observed. This was confirmed by an increase in TTX-resistant channels and by Western blot test. These channels exhibited increased activation time constant (tau(m)) and reduced conductance, similar to what has been observed in denervated muscles in vivo, where the density of Na(V)1.5 was increasing progressively after denervation. By real-time polymerase chain reaction, we found that the expression of beta subunits was also modified, but only after 7 days of culture: increase in beta(1) without beta(4) modifications. beta(1) subunit is known to induce a negative shift of the inactivation curve, thus reducing current amplitude and duration. At day 7, tau(h) was back to normal and tau(m) still increased, in agreement with a decrease in sodium current and conductance at day 4 and normalization at day 7. Our model is a useful tool to study the effects of denervation in adult muscle fibers in vitro and the expression of sodium channels. Our data evidenced an increase in Na(V)1.5 channels and the involvement of beta subunits in the regulation of sodium current and fiber excitability.
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10
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Boulais N, Pennec JP, Lebonvallet N, Pereira U, Rougier N, Dorange G, Chesné C, Misery L. Rat Merkel cells are mechanoreceptors and osmoreceptors. PLoS One 2009; 4:e7759. [PMID: 19898622 PMCID: PMC2770322 DOI: 10.1371/journal.pone.0007759] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Accepted: 10/13/2009] [Indexed: 01/15/2023] Open
Abstract
Merkel cells (MCs) associated with nerve terminals constitute MC-neurite complexes, which are involved in slowly-adapting type I mechanoreception. Although MCs are known to express voltage-gated Ca2+ channels and hypotonic-induced membrane deformation is known to lead to Ca2+ transients, whether MCs initiate mechanotransduction is currently unknown. To answer to this question, rat MCs were transfected with a reporter vector, which enabled their identification. Their properties were investigated through electrophysiological studies. Voltage-gated K+, Ca2+ and Ca2+-activated K+ (KCa) channels were identified, as previously described. Here, we also report the activation of Ca2+ channels by histamine and their inhibition by acetylcholine. As a major finding, we demonstrated that direct mechanical stimulations induced strong inward Ca2+ currents in MCs. Depolarizations were dependent on the strength and the length of the stimulation. Moreover, touch-evoked currents were inhibited by the stretch channel antagonist gadolinium. These data confirm the mechanotransduction capabilities of MCs. Furthermore, we found that activation of the osmoreceptor TRPV4 in FM1-43-labeled MCs provoked neurosecretory granule exocytosis. Since FM1-43 blocks mechanosensory channels, this suggests that hypo-osmolarity activates MCs in the absence of mechanotransduction. Thus, mechanotransduction and osmoreception are likely distinct pathways.
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Affiliation(s)
- Nicholas Boulais
- University of Brest, European University of Brittany, Laboratory on Nervous Factors and Tissular Structure, EA4326, CHU, Brest, France
- Bioprédic International, Rennes, France
| | - Jean-Pierre Pennec
- University of Brest, European University of Brittany, Laboratory on Nervous Factors and Tissular Structure, EA4326, CHU, Brest, France
| | - Nicolas Lebonvallet
- University of Brest, European University of Brittany, Laboratory on Nervous Factors and Tissular Structure, EA4326, CHU, Brest, France
| | - Ulysse Pereira
- University of Brest, European University of Brittany, Laboratory on Nervous Factors and Tissular Structure, EA4326, CHU, Brest, France
| | | | - Germaine Dorange
- University of Brest, European University of Brittany, Laboratory on Nervous Factors and Tissular Structure, EA4326, CHU, Brest, France
| | | | - Laurent Misery
- University of Brest, European University of Brittany, Laboratory on Nervous Factors and Tissular Structure, EA4326, CHU, Brest, France
- * E-mail:
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Effects of chronic sepsis on contractile properties of fast twitch muscle in an experimental model of critical illness neuromyopathy in the rat. Crit Care Med 2008; 36:1855-63. [PMID: 18520643 DOI: 10.1097/ccm.0b013e318176106b] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Critical illness polyneuromyopathy has been extensively studied in various animal models regarding electrophysiological aspects or molecular mechanisms involved in its physiopathology; however, little data are available on its main clinical feature, that is, muscular weakness. We have studied the effects of chronic sepsis in rats with special consideration to contractile and neuromuscular blockade properties in relation with the level of messenger RNA (mRNA) coding for ryanodine and acetylcholine receptors. DESIGN This was an experimental animal study. SETTING This study was conducted at a university laboratory. SUBJECTS Subjects consisted of Wistar rats. INTERVENTIONS Chronic sepsis was achieved by cecal ligation and needle perforation. Ten days after surgery, fast twitch extensor digitorum longus was excised for extraction and assays of mRNA coding for ryanodine and acetylcholine receptor subunits and contralateral muscle was tested in vivo on a mechanical bench. A fatigability index was measured and neuromuscular blockade properties using atracurium were evaluated. MEASUREMENTS AND MAIN RESULTS A decrease in active force developed by extensor digitorum longus associated with an increase in passive force is induced by chronic sepsis. Maximal force at optimal length during twitch contraction was significantly reduced (0.25 +/- 0.09 N vs. 0.17 +/- 0.06 N); contraction and relaxation speeds were higher as shown by the decrease of respective time constants (3.75 +/- 0.01 msec vs. 2.70 +/- 0.0 msec, 10.76 +/- 0.03 msec vs. 7.62 +/- 0.03 msec) in the control group compared with the septic group. Fatigability index was significantly lower (23 +/- 0.11% vs. 59 +/- 0.19%) in septic rats. These rats also showed quicker blockade and shorter recovery after atracurium administration. Sepsis induced a significant increase of the expression of ryanodine receptor (RyR) RyR1 along with a steady expression of RyR3 mRNA, leading to a 5.6-fold increase of RyR1/RyR3 ratio with a steadiness of mRNA corresponding to acetylcholine-receptors. CONCLUSIONS Chronic inflammation and sepsis induced a decrease in contractile performances of extensor digitorum longus along with accelerated kinetics of atracurium possibly induced by modified expression of RyR1 receptors and not acetylcholine-receptors.
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Endotoxin reduces availability of voltage-gated human skeletal muscle sodium channels at depolarized membrane potentials. Crit Care Med 2008; 36:1239-47. [PMID: 18379251 DOI: 10.1097/ccm.0b013e31816a02cf] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Critical illness myopathy is a common cause for difficulties in weaning from the respirator and prolonged rehabilitation of patients recovering from sepsis. Several studies have shown that the primary cause of acute generalized muscle weakness is loss of muscle membrane excitability. This study was designed to investigate a potential direct interaction of lipopolysaccharides from Escherichia coli with voltage-gated human skeletal muscle sodium channels (NaV1.4) in vitro. DESIGN In vitro laboratory investigation. SETTING University laboratory. SUBJECTS NaV1.4 sodium channel alpha-subunits stably expressed in human embryonic kidney (HEK293) cells. INTERVENTIONS We investigated the effect of lipopolysaccharide on voltage-dependent sodium channel gating by using two distinct modes of application: 1) acute perfusion (pharmacologic lipopolysaccharide concentrations between 5 ng/mL and 50 microg/mL) in order to establish a concentration-effect relationship; and 2) incubation with a clinically relevant concentration of lipopolysaccharide (300 pg/mL). MEASUREMENTS AND MAIN RESULTS Lipopolysaccharide did not alter the kinetics of sodium current activation or inactivation when depolarizations were started from hyperpolarized holding potentials. However, when either fast or slow inactivation was induced by membrane depolarization before the test pulse, lipopolysaccharide reversibly reduced channel availability during the test pulse at concentrations of > or = 50 ng/mL revealed by a maximum hyperpolarizing shift of -25 mV in the voltage dependence of fast and slow inactivation, respectively. Incubation with a lipopolysaccharide concentration of 300 pg/mL for 1 hr reproduced the effects on slow but not on fast inactivation. After 20 hrs of low-dose lipopolysaccharide, the peak sodium current was significantly reduced. CONCLUSIONS Our results show that lipopolysaccharide interacts with voltage-gated sodium channels, reducing channel availability at depolarized membrane potentials during acute application, independent of the membrane potential after chronic exposure. These effects may contribute to reduced muscle membrane excitability in sepsis.
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Rossignol B, Gueret G, Pennec JP, Morel J, Giroux-Metges MA, Talarmin H, Arvieux CC. Effects of chronic sepsis on the voltage-gated sodium channel in isolated rat muscle fibers. Crit Care Med 2007; 35:351-7. [PMID: 17205014 DOI: 10.1097/01.ccm.0000254335.88023.0e] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Physiopathology of critical illness polyneuromyopathy was investigated in several animal-based models. Electrophysiologic approach was achieved in denervated and corticosteroid-induced myopathy; other models based on sepsis or inflammatory factors (zymosan, cytokines) were also used but did not consider voltage-gated sodium channel implication in neuromuscular weakness. We have studied electrophysiologic effects of chronic sepsis on an intact neuromuscular rat model with special consideration to the subtypes of sodium channels involved. DESIGN Experimental animal study. SETTING University laboratory. SUBJECTS Wistar rats. INTERVENTIONS Chronic sepsis was achieved by a technique of cecal ligature and needle perforation. Ten days after surgery, the rats were killed. Fast-twitch flexor digitorum brevis was excised and dissociated in 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid-buffered saline supplemented with 3.0 mg/mL collagenase. Fast sodium currents were recorded by a macropatch clamp technique at room temperature (22+/-2 degrees C) in a cell-attached configuration. MEASUREMENTS AND MAIN RESULTS A decrease in maximal sodium current and in conductance was evidenced without modification of the sodium Nernst potential. A shift of the voltage inactivation curve toward more negative potentials could explain the observed decrease in excitability. In parallel, we observed an up-regulation of NaV 1.5-type sodium channels. CONCLUSIONS Chronic inflammation and sepsis induced modifications of sodium channel properties that could contribute to muscular inexcitability. This inexcitability can be elicited by a modification of properties or type of voltage-gated sodium channels. Our results lead us to explain this inexcitability by an up-regulation of NaV 1.5 sodium channel.
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Affiliation(s)
- Benoit Rossignol
- Département d'Anesthésie Réanimation, University Hospital of Brest, Brest, France
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Midrio M. The denervated muscle: facts and hypotheses. A historical review. Eur J Appl Physiol 2006; 98:1-21. [PMID: 16896733 DOI: 10.1007/s00421-006-0256-z] [Citation(s) in RCA: 108] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/11/2006] [Indexed: 01/09/2023]
Abstract
Denervation changes in skeletal muscle (atrophy; alterations of myofibrillar expression, muscle membrane electrical properties, ACh sensitivity and excitation-contraction coupling process; fibrillation), and their possible causes are reviewed. All changes can be counteracted by muscle electrostimulation, while denervation-like effects can be caused by the complete conduction block in muscle nerve. These results do not support the hypothesis that the lack of neurotrophic, non-motor factors plays a role in denervation phenomena. Instead they support the view that the lack of neuromotor discharge is the only cause of the phenomena and that neuromotor activity is an essential factor in regulating muscle properties. However, some experimental results cannot apparently be explained by the lack of neuromotor impulses, and may still suggest that neurotrophic influences exist. A hypothesis is that neurotrophic factors, too feeble to maintain a role in completely differentiated, adult muscles, can concur with neuromotor activity in the differentiation of immature, developing muscles.
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Affiliation(s)
- Menotti Midrio
- Department of Human Anatomy and Physiology, Section of Physiology, University of Padua, via Marzolo 3, Padova, Italy.
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Wu WKK, Li GR, Wong HPS, Hui MKC, Tai EKK, Lam EKY, Shin VY, Ye YN, Li P, Yang YH, Luo JC, Cho CH. Involvement of Kv1.1 and Nav1.5 in proliferation of gastric epithelial cells. J Cell Physiol 2006; 207:437-44. [PMID: 16331678 DOI: 10.1002/jcp.20576] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In the present study, patch clamp experiments demonstrated the expression of multiple ionic currents, including a Ba2+-sensitive inward rectifier K+ current (IKir), a 4-aminopyridine- (4-AP) sensitive delayed rectifier K+ current (IKDR), and a nifedipine-sensitive, tetrodotoxin-resistant inward Na+ current (INa.TTXR) in the non-transformed rat gastric epithelial cell line RGM-1. RT-PCR revealed molecular identities of mRNAs for the functional ionic currents, including Kir1.2 for IKir, Kv1.1, Kv1.6, and Kv2.1 for IKDR, and Nav1.5 for INa.TTXR. Pharmacologic blockade of Kv and Nav, but not Kir, suppressed RGM-1 cell proliferation. To further elucidate which subtypes of the ion channels were involved in cell proliferation, RNA interference was employed to knockdown specific gene expression. Downregulation of Kv1.1 or Nav1.5 by RNA interference suppressed RGM-1 cell proliferation. To conclude, our study is the first to delineate the expression of ion channels and their functions as growth modulators in gastric epithelial cells.
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Affiliation(s)
- William Ka Kei Wu
- Department of Pharmacology, Faculty of Medicine, The University of Hong Kong, Hong Kong, China
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Zaldivar D, García MC, Sánchez JA. Ciliary neurotrophic factor promotes inactivation of muscle Ca2+ channels via PKC. Biochem Biophys Res Commun 2005; 338:1572-7. [PMID: 16274672 DOI: 10.1016/j.bbrc.2005.10.125] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2005] [Accepted: 10/21/2005] [Indexed: 01/15/2023]
Abstract
The actions of the ciliary neurotrophic factor (CNTF) were assessed on adult mouse skeletal muscle L-type Ca2+ currents and on Ca2+ release from sarcoplasmic reticulum. Currents were measured with the whole cell patch clamp technique. Ca2+ signals in response to single action potentials were recorded with Fluo3-AM. CNTF (20 ng/ml) reversibly reduced the amplitude of Ca2+ channel currents by 50% within 15 min. In addition, CNTF greatly increased the rate of inactivation during depolarizing pulses and shifted the steady state inactivation curve by -12 mV. The effects of CNTF were mimicked by the PKC activator PMA and prevented by the PKC-inhibitor chelerythrine. In contrast to the effects on the Ca2+ conductance, charge movement and Ca2+ signals remained unaffected by CNTF. These results suggest that CNTF can rapidly decrease muscle Ca2+ channel currents by promoting inactivation, probably through an intracellular PKC-dependent mechanism.
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Affiliation(s)
- Daniel Zaldivar
- Departmento de Farmacología, Centro de Investigación y de Estudios Avanzados del I.P.N., México, DF 07360, Mexico
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